The invention relates to a picture display device suitable for receiving and processing an incoming video signal which comprises horizontally scanned picture information and for displaying pictures which are composed of fields each of which comprises a given number of lines, said device comprising a scanning section for generating line and field scanning signals for forming the lines and fields, respectively, and a video signal processing section for processing the picture information which is present in the video signal.
In such commonly known picture display devices the picture is formed in that lines are substantially horizontally scanned from left to right, for example on the display screen of a picture display tube, while picture information is applied to electrodes of the tube. Thus, picture information is assigned to the elements of the horizontally scanned lines. The successive lines are scanned from top to bottom so that a given number of lines forms a field. A frame comprises two or more fields, or, alternatively, a picture is formed by one field. For example, according to the European television broadcasting standard a frame is composed of 2 interlaced fields of 3121/2 lines each, the field frequency being 50 Hz and the line frequency being 15,625 Hz. Scanning at the signal source in the studio is identical to scanning upon display. This is ensured by synchronizing signals which are transmitted together with the picture information.
In picture display devices for displaying digitally generated text, so-called monitors, the line frequency may be higher than the frequency prescribed by a television standard. So-called high-definition television (HDTV) systems are also proposed in which the line frequency in the display device is very high, for example 62.5 kHz, which is 4 times as high as the line frequency in the current television standard. As a result, the energy dissipation in the line scanning circuits, i.e. losses caused by eddy currents, by the hysteresis of magnetic materials and in switching elements, is considerably larger. The dissipation at the line deflection in a cathode ray tube has been described for different values of the line frequency in the Article "Practical Considerations in the Design of Horizontal Deflection Systems for High-Definition Television Displays", published in the journal "IEEE Transactions on Consumer Electronics", Vol. CE-29, No. 3, Aug. 1983, pp. 334 to 349. It appears from this publication that an increase of the line frequency from 15.75 kHz (American television standard) to 63 kHz at an aspect ratio of 4:3 of the displayed image and a 110.degree. cathode ray tube with a final anode voltage of 30 kV leads to an increase of the transistor losses from 1.4 to 4.3 W to 35 to 165 W (dependent on the turn-off time), while the total losses in the deflection yoke increase from 7.5 W to 40 to 50 W and the losses caused by the eddy currents and the hysteresis increase from approximately 3.5 to 36 to 46 W (dependent on the yoke material). These figures show the importance of the problem posed by the dissipation.